Optical reading or writing apparatus

Abstract

An information-carrying medium having the form of a disc is rotated around a central axis. The temperature of the disc is controlled by a temperature-adjusting element facing the surface of the disc.

What is claimed is: 
     
       1. An optical reading or writing apparatus comprising an information-carrying medium on which information can be read or written optically, the information-carrying medium having the form of a disc rotating around a central axis and receiving a light beam from an optical head that is driven in the radial direction of the disc,   a detection means located near the information-carrying medium, for detecting the angle between the optic axis of the light beam and the surface of the information-carrying medium,   a temperature-adjusting element located near and facing the surface of the information-carrying medium, for creating a temperature difference between the two surfaces of the information-carrying medium and thereby causing a thermal deformation that bends the information-carrying medium in a desired direction, and   a control circuit for receiving a signal from the detection means and controlling the temperature-adjusting element by supplying energy to it in such a way as to maintain a perpendicular relationship between the surface of the information-carrying medium and the optic axis.   
     
     
       2. An optical reading or writing apparatus as set forth in claim 1, wherein the temperature-adjusting element is located facing the information-carrying medium near its circumference.   
     
     
       3. An optical reading or writing apparatus as set forth in claim 1, wherein the detection means is located at the circumference of the information-carrying medium.   
     
     
       4. An optical reading or writing apparatus as set forth in claim 1, wherein the temperature-adjusting element comprises a plurality of elements which are disposed at different radial positions to create a temperature difference along the radial direction on a surface of the information-carrying medium.   
     
     
       5. An optical reading or writing apparatus as set forth in claim 4, wherein the detection means comprises an inner means and an outer means which are positioned in radially inner and outer regions of the information-carrying medium, respectively.   
     
     
       6. An optical reading or writing apparatus as set forth in claim 1, wherein the temperature-adjusting element comprises a heating element and a cooling element disposed on opposite sides of the information-carrying medium.   
     
     
       7. An optical reading or writing apparatus as set forth in claim 1, wherein the temperature-adjusting element is a semiconductor element employing the Peltier effect.   
     
     
       8. An optical reading or writing apparatus as set forth in claim 1, wherein the temperature-adjusting element is also used to remove condensed moisture.   
     
     
       9. An optical reading or writing apparatus as set forth in claim 1, wherein the detection means is driven in the radial direction to detect said angle at different positions along the radial direction.